Liquid-chromatographic assay for urinary 3-methoxy-4-hydroxymandelic acid, with use of a periodate oxidative monitor.

We describe a "high-performance" liquid-chromatographic procedure for measuring 3-methoxy-4-hydroxymandelic acid (vanillylmandelic acid) in urine. The compound is quantitatively extracted from urine by use of an automated system, including an anion-exchange resin. After elution from the resin and concentration by air drying, the urine extract is chromatographed on an octyl silica column, with use of a buffered mobile phase. To overcome interference from other organic acid in the extract, the column effluent is reacted with periodate in an analytical system to oxidize the analyte and internal standard to products that absorb at 360 nm. We evaluated the procedure for precision, linearity, analytical recovery, interfering substances, and correlation with an established procedure. The combination of a preliminary resin extraction, a liquid-chromatographic separation, and a periodate oxidative monitor results in a rapid, specific method that can be adapted for use in the clinical laboratory.